powerpc: Hard wire PT_SOFTE value to 1 in ptrace & signals

We have always had softe in pt_regs, and accessible via PT_SOFTE, even
though it is not userspace state.

The value userspace sees should always be 1, because we should never
be in userspace with interrupts soft disabled.

In a subsequent patch we will be changing the semantics of the kernel
softe value, so hard wire the value to 1 to retain the existing
semantics. As far as we know nothing ever looks at it, but better safe
than sorry.
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
[mpe: Split out of larger patch, write change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/ptrace.c

@@ -283,6 +283,18 @@ int ptrace_get_reg(struct task_struct *task, int regno, unsigned long *data)
 	if (regno == PT_DSCR)
 		return get_user_dscr(task, data);
 
+#ifdef CONFIG_PPC64
+	/*
+	 * softe copies paca->soft_enabled variable state. Since soft_enabled is
+	 * no more used as a flag, lets force usr to alway see the softe value as 1
+	 * which means interrupts are not soft disabled.
+	 */
+	if (regno == PT_SOFTE) {
+		*data = 1;
+		return  0;
+	}
+#endif
+
 	if (regno < (sizeof(struct pt_regs) / sizeof(unsigned long))) {
 		*data = ((unsigned long *)task->thread.regs)[regno];
 		return 0;

arch/powerpc/kernel/signal_32.c

@@ -111,12 +111,20 @@ static inline int save_general_regs(struct pt_regs *regs,
 {
 	elf_greg_t64 *gregs = (elf_greg_t64 *)regs;
 	int i;
+	/* Force usr to alway see softe as 1 (interrupts enabled) */
+	elf_greg_t64 softe = 0x1;
 
 	WARN_ON(!FULL_REGS(regs));
 
 	for (i = 0; i <= PT_RESULT; i ++) {
 		if (i == 14 && !FULL_REGS(regs))
 			i = 32;
+		if ( i == PT_SOFTE) {
+			if(__put_user((unsigned int)softe, &frame->mc_gregs[i]))
+				return -EFAULT;
+			else
+				continue;
+		}
 		if (__put_user((unsigned int)gregs[i], &frame->mc_gregs[i]))
 			return -EFAULT;
 	}

arch/powerpc/kernel/signal_64.c

@@ -110,6 +110,8 @@ static long setup_sigcontext(struct sigcontext __user *sc,
 	struct pt_regs *regs = tsk->thread.regs;
 	unsigned long msr = regs->msr;
 	long err = 0;
+	/* Force usr to alway see softe as 1 (interrupts enabled) */
+	unsigned long softe = 0x1;
 
 	BUG_ON(tsk != current);
 
@@ -169,6 +171,7 @@ static long setup_sigcontext(struct sigcontext __user *sc,
 	WARN_ON(!FULL_REGS(regs));
 	err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
 	err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
+	err |= __put_user(softe, &sc->gp_regs[PT_SOFTE]);
 	err |= __put_user(signr, &sc->signal);
 	err |= __put_user(handler, &sc->handler);
 	if (set != NULL)